I. Field of the Invention
The present invention pertains to robotically operated laser cutting and welding devices. More particularly, the present invention pertains to a robotically controlled laser cutting or welding head that operates about the surface of a three dimensional workpiece.
II. Prior Art
Present-day laser cutting or welding devices typically have a light source that directs light to one or more mirrors and lenses which in turn directs the light to a focal or condenser optic. The light source may be an optic fiber. The mirror and lenses or optics of the laser device are typically housed in a laser head. The laser head has a housing with a nozzle through which a laser beam is directed to impinge upon a workpiece. The operation or motion of the laser head about a workpiece may be controlled by a robot and controller or the like.
Robotically controlled laser devices are often operated under rugged conditions. The devices are subjected to jarring, bumping and vibrations. Continual use under these conditions often results in the light beam being other than optimally aligned on the laser optics.
Centering the light beam on the laser optics is important where light converges from the focal lens through the nozzle onto a work piece to deliver large amounts of energy. A focal lens is often used to concentrate such light from the light source into a powerful beam to cut or weld various materials. The most intense part of the beam is the apex or focal spot. The apex or focal spot impinges upon a workpiece to perform much of the laser operation. It is therefor necessary to maintain an optimal portion of the incoming light beam upon the focal lens to thereby maximize the operation of the focal spot upon a workpiece.
Additionally, replacement of the light source is not uncommon. Once a new light source is installed, the light beam is typically aligned upon each mirror or lens in the optic system. Care must be taken not to significantly alter the optimal path length of light diverging from the light source to avoid diminishing the intensity of the concentrated laser beam. Care must also be exercised to direct the concentrated light beam through the nozzle of the laser head. Thus, the installation of a new light source is often time consuming, laborious, and requires considerable care.
Realignment of the optics in many present day laser heads mandates that the head be dismantled and each mirror or lens be individually adjusted. Laser cutting operations may not be performed in the cleanest environments. Thus, the laser head must be removed from the operation site to a clean location so that the laser optics can be adjusted in a contamination free environment. The realignment process, like the installation process, is also time-consuming, laborious and requires considerable care so as not to contaminate the optics with dirt and dust.
Some laser heads provide a way to realign the laser beam by adjusting the focal or condenser lens. In such laser heads, a mechanism for adjusting the condenser lens is disposed near or at the nozzle. A laser head having a mechanism for adjusting the condenser lens is disadvantageous for a number of reasons. One such reason is that the mechanism for adjusting the condenser lens results is a laser head having a bulky housing and nozzle. The bulky housing and nozzle is particularly disadvantageous where the laser head must be manipulated about the surface of a three-dimensional workpiece having varying topography.
Furthermore, assist or make-up gases, such as oxygen, are used with lasers to increase the laser""s cutting efficiency and for removing debris from the cutting surface. The assist gas is typically delivered from the nozzle of the laser head to the surface of a workpiece. The gas may be delivered to the nozzle via an external, loose tube or hose connected to a gas source. The gas delivery tubes of present day laser heads are deficient for a number of reasons including the fact that they create a point or place for a workpiece to catch upon. Additionally, these tubes frequently wear out or become damaged as a result of their external positioning next the laser head, thus requiring repeated replacement.
As is generally known to the skilled artisan, present day laser heads can be operated by a robot. The robot controls the pattern and distance the laser head operates about the surface of a workpiece.
The surface topography of a workpiece can vary considerably. Similarly, the thickness of a workpiece can also vary considerably. As a result, it has been a long-standing problem to have collisions between the laser head and a workpiece or a surrounding fixture that may damage either the laser head or the workpiece. To further complicate the problem, workpieces are often cut in batch during industrial operations. As a robot moves the laser head from workpiece to workpiece collisions may occur due to the misplacement of the workpiece within a support structure.
One attempt to overcome the problem of collisions has been to provide present day laser heads with breaker switches or micro switches that open to stop the robot after a laser head has collided with a workpiece. The force required to open the breaker switch may be a force sufficient to disconnect the laser head from the robot. This force can be sufficient to damage the laser head, optics or the robot.
Therefore, it is to be appreciated from the preceding that present day robotically operated laser heads are deficient in providing for precise manipulation about a three-dimensional workpiece having varying topography for a number of reasons. For example, present day laser heads require a bulky housing to accommodate present day optics and their support structures. Further, present day laser heads are typically fitted with an external assist gas delivery system that may catch upon a workpiece or fixture and may succumb to accelerated wear.
It is also to be appreciated from the preceding that present day robotically operated laser heads fail to provide a suitable means for adjusting the optical path of a light source upon a condenser optic to focus a laser beam through a nozzle of the laser head.
It is also to be appreciated from the preceding that present day robotically operated laser heads fail to provide an effective, yet durable, way of delivering an assist gas to the nozzle of a laser head.
It is also to be appreciated from the preceding that present day, robotically operated laser devices having a laser head attached to a robot are deficient in providing an effective means of avoiding a collision with a workpiece so as not to substantially disconnect the laser head from the robot attached thereto.
As discussed hereinbelow, the present invention, to address the above stated problems and others, as is detailed hereinafter, enables an improved laser head for manipulation about a three-dimensional workpiece having varying topography. The present invention also provides an improved laser device having means for avoiding a collision with a workpiece by stopping the robot and laser head operation before damage to the laser head or robot occurs.
The laser head hereof has: a housing; a nozzle attached to the housing at a distal end thereof, the nozzle forming a tip, a light source which produces a light beam supported by the housing; at least one focal optic for receiving the light beam and focusing the light beam into a high density laser beam through the nozzle, means for adjusting the light path of the light beam from the light source within the housing onto the focal optic wherein the means for adjusting is adapted to center the focusing beam coaxial with the tip, and means for adjusting the means for receiving the light beam.
The laser head may further include means for delivering an assist gas from inside the housing, through the nozzle to the cutting surface of a workpiece. Also, the laser head may further comprise means for determining the proximity of the laser head to a workpiece.
By delivering an assist gas from within the housing and placing the means for adjusting the means for receiving the light beam within a top portion of the housing, the nozzle and the laser head may be formed with a more streamlined design. By making the housing and the nozzle more streamlined, the laser head can be operated more precisely about the surface of a three-dimensional workpiece.
The present invention also provides means for avoiding a collision between a laser head and a workpiece. Robotic operation of the laser head may be performed in several modes. The modes of operation may be determined by either the proximity of the laser head to a surface of a work piece or the operating condition of the robotic unit or both. The modes of operation may include, for example, an operation or run mode, a park mode, a teach mode, and a hold mode. The modes of operation may further be controlled by the operating condition of the laser head, for instance, whether the laser head is operating at an extended or a retracted limit.
In use the laser head is mounted to a robot or robotic arm, which together, function as a laser device that may operate upon a surface of a workpiece in one or more of the above mentioned modes. The laser device has means for determining if the laser head is in contact with or in close proximity to the surface of the workpiece. Depending upon the mode of operation that the laser device is functioning in, the device, particularly the robot operation, will cease to operate when the laser head is at a predetermined distance from a workpiece. Thus, by prohibiting the device from operating in certain modes when the laser head is positioned above a surface of a workpiece at a certain distance, the present invention provides a crash avoidance system whereby the laser head is less likely to be involved in a crash with a workpiece to prevent damage and other problems that may therefor follow.
The laser head hereof may be telescopable. In operation, the telescopable laser head retracts and extends to follow the surface of a workpiece and to correct for minor deviations therein. The crash avoidance system provides means for stopping the laser head and robot or the laser device when the telescopable laser head reaches an extended limit or a retracted limit.
The laser head will typically reach an extended limit when the laser head is fully telescoped and positioned at a maximum distance from a work piece such that the laser head can not extend further to accommodate the distance from a workpiece that the laser head is operating at. Even though the laser head is not likely to be involved in a collision with a work piece at this distance, such distance is likely to result in inferior use of the laser. Therefore, the robot is better shut down or stopped then left to continued operation about a workpiece.
The laser head reaches a retracted limit when the laser head moves so close to a workpiece that the laser head may no longer retract within itself. The laser head may reach a retracted limit for a number of reasons, for example as a result of operating programming which does not coincide with the variations among surface topography between workpieces. If a laser head is left to operate at a retracted limit, the laser beam may not optimally impinge upon the surface of the workpiece. Additionally, the laser head will be more prone to crashing when operating at a retracted limit. Therefore, the robot and laser head are preferably stopped until adjustments, such as reprogramming the robot or repositioning the work piece, may be preformed.
For a more complete understanding of the present invention, reference is made to the following detailed description and accompanying drawings. In the drawings like reference characters refer to like parts throughout the several views.